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Avalanche Forecast

Archived

Nov 19th, 2023–Nov 20th, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Early Season
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Early Season
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Early Season

Regions

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

As strong winds in the alpine persist, wind slabs will remain reactive. Watch for strong winds and associated slab development locally, on climbs or out sliding on the snow.

It is still very much "low tide" in the Rockies, as Early Season Conditions exist.

Confidence

Moderate

Avalanche Summary

We are still receiving reports of recent natural and explosive triggered avalanches up to size 2. The persistent slab will be with us for a while and should be treated with respect. There have been reports of remotely triggering avalanches from 300m away.

Wind slab formation is likely to continue with strong winds in the forecast. These slabs are very likely to step down to the persistent slab if triggered. Pay attention to wind and snowfall amounts locally.

Snowpack Summary

It's still early season with only 30-50 cm at tree-line and 40-80 cm in the alpine. Many early season hazards lurk just below the snow surface.

Wind slab's continue to be sensitive to human triggering. If triggered it is very possible that they step down to the bottom of the snowpack causing larger avalanches.

Lake Louise ski hill reported a new crust from solar activity yesterday on the surface of south and west aspects, below 2500m.

Forecaster have limited observations.

Weather Summary

Winds will continue to be very strong in the alpine down into treeline this evening, through tomorrow. Mild temperatures will persist through the region, as forecaster call for a trace amount of snow overnight. Alpine high is -5C tomorrow, as valley bottoms peak at 0C. Mainly sunny skies on Monday.

For more info, please see the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Ice climbers should be equipped with avalanche safety gear.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.